filter!(not!(predicate))(someInputRange) does not compile

[Jens K. Mueller]

Andrei Alexandrescu wrote:
> On 1/20/11 12:47 PM, Jens Mueller wrote:
> >Andrei Alexandrescu wrote:
> >>On 1/19/11 7:19 PM, Jens Mueller wrote:
> >>>Andrei Alexandrescu wrote:
> >>>>Place the call to not!alwaysTrue in a local function inside main:
> >>>>
> >>>>     bool alwaysFalse(uint a) { return not!alwaysTrue(a); }
> >>>
> >>>Thanks. Can you elaborate a bit please? I wonder why the alias won't
> >>>work.
> >>
> >>I thought of it for a bit. It's a limitation of the compiler that's
> >>worth a bug report. The explanation is a bit involved. Let me start
> >>by remarking that if you prepend "static" to alwaysTrue, the alias
> >>works as expected:
> >>
> >>static bool alwaysTrue(uint a) { return true; }
> >>alias not!(alwaysTrue) alwaysFalse;
> >>
> >>Without "static", alwaysTrue has access to a hidden pointer to the
> >>stack frame of the function is in.
> >
> >Yeah. That makes sense.
> >It has this hidden pointer to access variables from the function it is
> >defined in.
> >
> >>In theory a template should be unable to manipulate alwaysTrue
> >>because of that frame pointer. But Walter has had this great idea of
> >>instantiating templates in the context of the function they're in,
> >>so they gain access to the frame pointer too. However, that
> >>instantiation mechanism still has a few limitations. I think the
> >>code above runs into one of them.
> >
> >I see.
> >I can file a bug report if it is considered important and should not be
> >forgotten.
> >
> >Jens
> 
> Yes please. Make it an enhancement as it would remove a limitation
> of an otherwise little explored feature. Thanks!

http://d.puremagic.com/issues/show_bug.cgi?id=5469